Higher and bigger:How riparian bats react to climate change

Highlights•In 2000–23, Daubenton's bats reacted to climate change along an altitude gradient.•Climate warmed, but habitat quality remained unchanged during this time.•Females shifted their elevational limit upward by 175 m.•Bats grew significantly larger, possibly due to more favourable roost temperatures.•Future risks: Social disruption and higher mortality in larger bats.AbstractThe altitudinal distribution of animals and changes in their body size are effective indicators of climate change. Bats are sensitive to climate change due to their dependence on temperature during critical life stages. However, long-term studies documenting responses over extended periods are rare. We present a 24-year investigation of Myotis daubentonii, a riparian bat known for altitudinal sexual segregation, along a river course in Central Italy. While males occupy the entire river course, females are confined to downstream warmer areas supporting successful reproduction due to improved foraging site productivity. In 2000, females were absent above 900 m a.s.l in our study area. We hypothesise that a) this altitude threshold is now higher, due to thermal gradient changes along the river course; and b) thermoregulatory costs for reproductive females have declined, leading to increased energy investment in offspring and subsequent generational growth in bat body size. Confirming our hypotheses, females exhibited a 175-m upward shift in altitude limit. Furthermore, we found a concurrent increase in body size (but not condition). Temperatures increased in the 24 years, likely allowing females to extend their range to higher elevations and favouring an increase in newborn body mass. Riparian vegetation remained unchanged, excluding habitat quality changes as the cause for the observed responses. The rapid female elevation rise might imply future disruption of established social structures, altering intra- and intersexual competition for roosts and food. Given the global decline in insect populations, larger bats might face future difficulties in finding food to sustain their body size, increasing mortality. However, the full impact of such changes on bat fitness remains unexplored and warrants further investigation, including other bat populations. This knowledge is crucial for informing conservation in the face of ongoing climate change and preserving the ecosystem services bats deliver in riparian ecosystems

Climate is changing, are European bats too?:A multispecies analysis of trends in body size

Animal size, a trait sensitive to spatial and temporal variables, is a key element in ecological and evolutionary dynamics. In the context of climate change, there is evidence that some bat species are increasing their body size via phenotypic responses to higher temperatures at maternity roosts. To test the generality of this response, we conducted a &gt;20-year study examining body size changes in 15 bat species in Italy, analysing data from 4393 individual bats captured since 1995. In addition to examining the temporal effect, we considered the potential influence of sexual dimorphism and, where relevant, included latitude and altitude as potential drivers of body size change. Contrary to initial predictions of a widespread increase in size, our findings challenge this assumption, revealing a nuanced interplay of factors contributing to the complexity of bat body size dynamics. Specifically, only three species (Myotis daubentonii, Nyctalus leisleri, and Pipistrellus pygmaeus) out of the 15 exhibited a discernible increase in body size over the studied period, prompting a reassessment of bats as reliable indicators of climate change based on alterations in body size. Our investigation into influencing factors highlighted the significance of temperature-related variables, with latitude and altitude emerging as crucial drivers. In some cases, this mirrored patterns consistent with Bergmann's rule, revealing larger bats recorded at progressively higher latitudes (Plecotus auritus, Myotis mystacinus, and Miniopterus schreibersii) or altitudes (Pipistrellus kuhlii). We also observed a clear sexual dimorphism effect in most species, with females consistently larger than males. The observed increase in size over time in three species suggests the occurrence of phenotypic plasticity, raising questions about potential long-term selective pressures on larger individuals. The unresolved question of whether temperature-related changes in body size reflect microevolutionary processes or phenotypic plastic responses adds further complexity to our understanding of body size patterns in bats over time and space.<br/

Sociality influences thermoregulation and roost switching in a forest bat using ephemeral roosts

In summer, many temperate bat species use daytime torpor, but breeding females do so less to avoid interferences with reproduction. In forest-roosting bats, deep tree cavities buffer roost microclimate from abrupt temperature oscillations and facilitate thermoregulation. Forest bats also switch roosts frequently, so thermally suitable cavities may be limiting. We tested how barbastelle bats (Barbastella barbastellus), often roosting beneath flaking bark in snags, may thermoregulate successfully despite the unstable microclimate of their preferred cavities. We assessed thermoregulation patterns of bats roosting in trees in a beech forest of central Italy. Although all bats used torpor, females were more often normothermic. Cavities were poorly insulated, but social thermoregulation probably overcomes this problem. A model incorporating the presence of roost mates and group size explained thermoregulation patterns better than others based, respectively, on the location and structural characteristics of tree roosts and cavities, weather, or sex, reproductive or body condition. Homeothermy was recorded for all subjects, including nonreproductive females: This probably ensures availability of a warm roosting environment for nonvolant juveniles. Homeothermy may also represent a lifesaver for bats roosting beneath loose bark, very exposed to predators, because homeothermic bats may react quickly in case of emergency. We also found that barbastelle bats maintain group cohesion when switching roosts: This may accelerate roost occupation at the end of a night, quickly securing a stable microclimate in the newly occupied cavity. Overall, both thermoregulation and roost-switching patterns were satisfactorily explained as adaptations to a structurally and thermally labile roosting environment

Indicators of sustainable forest management: application and assessment

Report of the international project Life ManForCBD

What story does geographic separation of insular bats tell? A case study on Sardinian Rhinolophids [Correction]

There is an error in the legend of Figure 3. Please see the correct Figure 3 legend here

Sensory ecology of water detection by bats: a field experiment.

Bats face a great risk of dehydration, so sensory mechanisms for water recognition are crucial for their survival. In the laboratory, bats recognized any smooth horizontal surface as water because these provide analogous reflections of echolocation calls. We tested whether bats also approach smooth horizontal surfaces other than water to drink in nature by partly covering watering troughs used by hundreds of bats with a Perspex layer mimicking water. We aimed 1) to confirm that under natural conditions too bats mistake any horizontal smooth surface for water by testing this on large numbers of individuals from a range of species and 2) to assess the occurrence of learning effects. Eleven bat species mistook Perspex for water relying chiefly on echoacoustic information. Using black instead of transparent Perspex did not deter bats from attempting to drink. In Barbastella barbastellus no echolocation differences occurred between bats approaching the water and the Perspex surfaces respectively, confirming that bats perceive water and Perspex to be acoustically similar. The drinking attempt rates at the fake surface were often lower than those recorded in the laboratory: bats then either left the site or moved to the control water surface. This suggests that bats modified their behaviour as soon as the lack of drinking reward had overridden the influence of echoacoustic information. Regardless of which of two adjoining surfaces was covered, bats preferentially approached and attempted to drink from the first surface encountered, probably because they followed a common route, involving spatial memory and perhaps social coordination. Overall, although acoustic recognition itself is stereotyped and its importance in the drinking process overwhelming, our findings point at the role of experience in increasing behavioural flexibility under natural conditions

The Buzz of Drinking on the Wing in Echolocating Bats

Bats broadcast rapid sequences of echolocation calls, named 'drinking buzzes', when they approach water to drink on the wing. So far this phenomenon has received little attention. We recorded echolocation sequences of drinking bats for 12 species, for 11 of which we also recorded feeding buzzes. Based on the different sensorial tasks faced by feeding and drinking bats, we hypothesize that the drinking buzz structure will differ from that of feeding buzzes since unlike the latter drinking buzzes are not designed to detect and track mobile prey. We demonstrated that drinking buzzes are structurally different from feeding buzzes. We show that the buzz-II phase common in feeding buzzes is absent in drinking buzzes; that is, call frequency is not lowered to broaden sonar beam since the task of drinking does not imply tracking fast-moving targets. This finding indirectly confirms the role of buzz II in feeding buzzes. Pulse rate in drinking buzzes is also lower than in feeding buzzes, as predicted since the high pulse rate typical of feeding buzzes is important to update rapidly the relative location of moving targets. The most likely function of drinking buzzes is to guide a safe drinking manoeuvre, similar to 'landing buzzes' broadcast when bats land on the ground

Roost selection by barbastelle bats (&lt;em&gt;Barbastella barbastellus&lt;/em&gt;, Chiroptera: Vespertilionidae) in beech woodlands of central Italy

The barbastelle bat, &lt;em&gt;Barbastella barbastellus&lt;/em&gt; (Schreber, 1774) is a medium-sized, tree-dwelling vespertilionid classified as ?Endangered? in Italy; in western Europe it may be one of the rarest bat species. &lt;em&gt;B. barbastellus&lt;/em&gt; shows roosting preferences that should be regarded as a key point in conservation protocols. We examined roost selection in a breeding population of &lt;em&gt;B. barbastellus&lt;/em&gt; from the Abruzzo Lazio and Molise National Park (central Italy) at three levels: woodland structure and management type; tree characteristics; and cavity characteristics. In 2001-2002, we fitted 31 adult &lt;em&gt;B. barbastellus&lt;/em&gt; (29 lactating females, one pregnant female and one male) with 0.48g radio-tags and tracked them to their roost-trees. The bats were tracked for 4.5 ± 3.7 days (range: 0-12 days). We located 33 roosts used by 25 subjects (1.8±1.2 roosts/bat, range 1-5). The bats switched roosts frequently: 13 bats used more than one tree over the study period. A chi-square analysis showed that the roosts were not distributed at random across woodland categories: unmanaged woodland was positively selected, whereas shelterwood-harvested woodland was used in proportion to its availability, and ?pastures+scattered trees? was avoided. Twenty out of 33 roost trees were dead &lt;em&gt;Fagus sylvatica&lt;/em&gt; trees; conversely, living &lt;em&gt;F. sylvatica&lt;/em&gt; dominated in a tree sample obtained at random; dead trees were used more than expected (&amp;#935;&amp;#178; test, &lt;em&gt;P&lt;/em&gt; &amp;#060;0.001). Overall, roost trees were significantly taller and had a larger diameter at breast?s height and more cavities than random trees; they also had a lower percent canopy closure than random trees. To highlight which variables were actually associated with selection, we devised a logistic regression model. The full model was significant (&lt;em&gt;P&lt;/em&gt; &amp;#060;0.001); removal of tree type and tree height affected the model significantly, but the other variables did not produce detectable effects. The bats roosted under loose bark in 20 of 27 trees, i.e. more frequently than expected (&amp;#935;&amp;#178; test, &lt;em&gt;P&lt;/em&gt; &amp;#060; 0.05). &lt;em&gt;B. barbastellus&lt;/em&gt; preferred cavities at a greater height (median roost height = 10.1 m, &lt;em&gt;n&lt;/em&gt; = 22; median random cavity height = 4.5 m, &lt;em&gt;n&lt;/em&gt; = 30; Mann-Whitney test, &lt;em&gt;P&lt;/em&gt; &amp;#060; 0.01). Most roosts faced south (63.6% south facing: 91-270 degrees; 36.4% north facing: 271-90 degrees, &lt;em&gt;n&lt;/em&gt; = 22; &amp;#935;&amp;#178; test, &lt;em&gt;P&lt;/em&gt; &amp;#060; 0.05). A logistic regression model including cavity type, height above ground and direction faced was significant (&lt;em&gt;P&lt;/em&gt; &amp;#060;0.01) and all variables were important for selection. &lt;em&gt;B. barbastellus&lt;/em&gt; is probably unable to find suitable roosting sites where intensive and non-selective logging is conducted: areas of ancient woodland should be protected to ensure optimal roosting conditions. In roosting areas, felling operations should be avoided as far as possible; in logged areas, selective timber harvesting protocols preserving dead trees and a significant fraction of mature trees should be adopted. We are indebted to the Nando Peretti Foundation and the Parco Nazionale d?Abruzzo Lazio e Molise for funding our work

Results of repeated measures General Linear Model ANOVA for the effect of watering trough covered, substrate type – water or Perspex – and site, on: a) the total number of drinking approaches to either surface (Perspex vs. water); b) the number of individual bats performing them; and c) the number of approaches per bat.

<p>Site was entered as a random factor. No interaction was significant so these were removed from final models. (*)  =  data log-transformed to meet the ANOVA assumptions; d.f.  =  degree of freedom.</p

Schematic bird’s eye view of watering troughs manipulated for the experiment at sites A, B and C.

<p>For each site one watering trough was covered with Perspex (grey rectangle), the other was left uncovered (white) so that water was available to bats. Two replicates of the experiment were done at each site, covering a different watering trough each time (left and right respectively). The arrows indicate the general direction (±45°) from which the bats approached the watering trough for drinking. Arrow width is proportional to the numbers of bats approaching from each direction (percent values are also given). Most bats always came from one side (and, in four out of six cases, one quadrant – see <i>P</i> values of Fisher’s exact tests in figure) and drank at the first watering trough encountered, so that the latter was disproportionately used over the other regardless of whether it had been covered with Perspex or not.</p